In studies associated with this project during the previous period of funding we have shown that colon carcinoma cell lines which are growth factor dependent and differentiated show weak tumorigenicity while progressed colon carcinoma cell lines which are strongly tumorigenic are growth factor independent. Autocrine TGF-beta activity provides the molecular basis for maintaining the growth factor dependency and weak tumorigenic properties of differentiated cells. Repression of autocrine TGF-beta activity by constitutive TGF-beta mRNA anti-sense expression led to growth factor independence and increased tumorigenicity by differentiated cells. The growth factor independence of undifferentiated progressed colon cancer cells is due to the expression of a strong TGF- alpha loop and the lack of TGF-beta autocrine activity. Removal of the TGF-alpha autocrine loop leads to growth factor dependency and reduction of tumorigenicity in these cells. An understanding of the mechanisms contributing to the maintenance of the TGF-beta autocrine activity of differentiated cells and the basis for the failure of this loop in progressed cells is critical to the potential development of therapeutic strategies which might lead to the conversion of progressed cells back to a more benign form. We and others have found that there are reciprocal relationships between expression of ECM and TGF-beta isoforms. The working hypothesis for this project is that ECM, integrins and autocrine TGF-beta expression interact to control the growth factor dependent phenotype. This hypothesis will be tested by the following specific aims. 1. Determine the role of ECM components in maintaining the growth factor dependent phenotype in growth factor dependent cells, 2. Determine the capability of ECM from growth factor dependent cells to impart the growth factor dependent phenotype to colon carcinoma cells which have intermediate properties with respect to the highly progressed cell lines and the growth factor dependent cell lines, 3. Determine the role of integrin expression in maintaining the growth factor dependent phenotype in growth factor dependent cells, 4. Determine whether the growth factor dependent phenotype of differentiated cells is dominant or recessive over the growth factor independent phenotype of highly progressed cells using complementation analysis.